The present disclosure relates to the field of pressure regulation for support devices having inflatable cells or compartments, such as, for example, therapeutic mattresses. Such mattresses are used in particular for beds for patients suffering from or presenting risks of developing skin pathologies of the decubitus ulcer or “bedsore” type due to them being kept immobile for prolonged periods in a sitting position or in a recumbent position. The present disclosure relates more particularly to a method of inflating, in alternating manner, inflatable cells of such a support device, and to a device for implementing the method.
In a support device having inflatable cells such as a therapeutic mattress, each inflatable cell communicates in substantially leaktight manner with at least one feed means for feeding an inflation fluid (conventionally, air) to the cells, via at least one electrovalve, such as a solenoid valve, that is itself connected to a control device for controlling inflation of the inflatable cells of the mattress and for regulating the air pressures inside said cells.
In practice, in order to fill/inflate the inflatable cells of the support device, air is fed into said cells until the desired pressures are reached. Conversely, in order to empty or deflate the inflatable cells or in order to adjust the inflation pressures, air is removed via a removal orifice provided for that purpose, and which sometimes is also provided with a solenoid valve that is controlled by the control device for controlling inflation.
Support devices of this type are used as mattresses for patient care because they make it possible to provide appropriate positioning of and appropriate support for the body on the surface of the mattress, as a function of the morphology and of the position of the patient.
In principle, ideal patient comfort and optimum blood circulation through the tissue for avoiding bedsore formation or for reducing local pain in certain zones of the body that bear against the mattress are obtained when the bearing points of the body are redistributed over the surface of the mattress, i.e. when the pressure exerted by the various zones of the body on the mattress (which pressure is referred to as the “interface pressure”) is substantially identical at all of the points of the surface of the body that are in contact with the mattress and if, in addition, the surface area of the body that is in contact with the mattress is as large as possible. This requires the degree to which the inflatable cells of the mattress are inflated under the various portions of the body to be adapted to control the depth to which the body penetrates into the various zones of the mattress.
For this purpose, the air pressures inside the inflatable cells are distributed by controlling the filling/emptying of said cells as a function, in particular, of measurements of stress exerted by the body of the patient on the mattress, which measurements are taken with sensors in, on, or sometimes below the mattress, depending on the type of sensors implemented. Such sensors are referred to below as “morphology sensors” and are known to the person skilled in the art. They measure, more particularly, a stress consisting in the “interface pressure”, i.e. the pressure exerted by the patient's body on the cells of the mattress, or the depth to which the patient's body penetrates into the cells of the mattress or the volume of immersion of the body of the patient into the cells of the mattress, as described, for example, in the Applicant's European Patent EP 0 676 158 and in the Applicant's European Patent EP 1 056 372. From those measurements, computation is used to deduce an appropriate regulation pressure for regulating the inflation of the cells as a function of the morphology of the patient on the mattress. The expression “morphology of the patient on the mattress” is used herein to mean both the mass of the patient and the contact surface area over which the patient is in contact with the mattress, i.e. the position of the patient on the mattress.
Controlling and regulating filling/emptying of the inflatable cells also makes it possible to obtain support devices that operate in an “alternating” inflation mode in which certain cells of the support device that are uniformly distributed along the length thereof are inflated and deflated simultaneously and in alternation. For example, one in every two cells are deflated and re-inflated, and then the cells adjacent to the previously deflated and re-inflated cells are deflated and re-inflated.
Thus, each inflatable cell of the support device is deflated/re-inflated in succession and progressively, thereby creating a sort of wave moving back and forth in the longitudinal direction of said support device and relieving the interface pressure locally, thereby locally facilitating blood circulation through the soft tissue at the interface with the surface of the support device.
In order to achieve such an alternating inflation mode for inflating the cells in alternation, current inflatable-cell support systems have inflation pressure control and regulation systems that incorporate complex electronic circuits for controlling the solenoid valves and inflation compressors and the like, such circuits including, inter alia, digital clocks and counters that have particularly high development and manufacturing costs and that are particularly voluminous. In addition, with currently known control and regulation systems, the alternating inflation and deflation cycle times are fixed, and left to the judgment of the designer or of the user.
The present disclosure relates to a method of inflating, in alternating manner, inflatable cells of a support device for supporting an element to be supported, which device is of the mattress type for supporting the body of a patient, said mattress being made up of cells that are inflatable with a fluid, in particular air, and having at least one zone made up of first and second series of inflatable cells referred to respectively as “first” cells and as “second” cells, the cells of each series communicating fluidly such as pneumatically, with one another and with inflation means, it being possible for the cells of each series of cells to be either in a state in which communication is open with the pump and with the cells of the other series of cells, or in a state in which communication is closed with the pump and with the cells of the other series and is open with the outside, in which state the cells are connected to the surrounding air, in which method alternating deflation and re-inflation cycles are performed during which each of said series of cells is deflated and then re-inflated in alternation and in succession, said first cells being deflated and then re-inflated simultaneously respectively with the re-inflation and with the deflation of said second cells, the alternating deflation and re-inflation steps for deflating and re-inflating, in alternation, said first and second cells of the support device including at least one step of inflating said cells to a value of at least one reference pressure Pc, PRmax, PRmin whose value is determined on the basis of a continuous measurement taken by means of a “morphology” sensor measuring the stress generated by the patient's body on the cells.
In patents EP 1 695 681 and EP 0 168 213, alternating inflation/deflation methods are described. However, in those two patents, the regulation pressure to which the cells are to be inflated is not determined by means of a sensor that directly measures the stress exerted by the body of the patient on the mattress, but rather it is deduced from measurements of pressure inside the cells, which is less reliable and less easy to implement.
More precisely, in Document EP 1 695 681, a predetermined alternating cycle time is set and the inflation pressure is determined as a function of a residual air pressure value measured inside the cells at the end of deflation during the cycle, after a predetermined given set time. Thus, in EP 1 695 681, it is possible to cause the inflation pressure of the cells to vary regularly during the cycle as a function of the morphology of the patient, but it is not possible to cause the inflation/deflation cycle time to vary automatically as a function of the morphology of the patient.
Finally, in EP 1 695 681, the cells are not deflated fully at the end of deflation, which is disadvantageous in terms of how well the blood circulates.
In EP 0 168 213, the regulation pressure or inflation pressure for the cells is determined on the basis of measurements of pressure inside the cells when the pressures in the various cells come to equilibrium during a calibration or initialization step before the alternating cycle proper starts. This calibration step must be repeated at regular intervals. In EP 0 168 213, no indication is given as to the implementation of the alternating inflation/deflation method subsequently to that initial calibration step.
Thus, in EP 1 695 681 and EP 0 168 213, the reference pressures to which the cells are to be inflated during an inflation/deflation cycle are determined as a function of the air pressures inside the cells as measured at regular intervals, which further requires a clock to be implemented.